#include<iostream>
#include<algorithm>
using namespace std;
int trans(char a)
{
	if (a == 'R') return 1;
	if (a == 'W') return 2;
	if (a == 'B') return 3;
}
bool cmp(char a, char b)
{
	return trans(a) < trans(b);
}

int main()
{
	int n;
	cin >> n;
	char a[n+1];
	cin >> a;
	sort(a, a+n, cmp);
	cout << a << endl;
	return 0;
}
